Self-Assembly Meets 3D Printing

Two technologies at the edges of manufacturing are on the verge of coming together: self-assembly and 3D printing. In a recent talk given at the 2013 TED conference, Skylar Tibbits, an MIT faculty member in architecture, demonstrated a new material and process that results in a 3D-printed object self-assembling underwater.

The new technology is a combination of Tibbits' process with Stratasys' materials and its Objet Connex 500 Multi Materials inkjet 3D printer, Daniel Dikovsky, digital materials team leader for Stratasys, told Design News. The idea for the material came when Dikovsky and Tibbits discussed Tibbits' self-assembly projects, which he had been activating via mechanical energy.

The material is a combination of two acrylic polymers, one water expandable and one an existing, static Vero black already used with the Connex 500 multi-material printer. "The combined material acts as a source of energy when placed in water, but it also serves as an actuator," Dikovsky told us. "When exposed to water, it absorbs water, expands, and changes its dimensions."

When exposed separately to water, the water-expandable material only expands and does not change its form, and the static material does not change at all. When they're combined, the geometry of the 3D printed shape can be programmed to change form in predictable ways. You can watch a video here showing a cube shape self-assembling in water from a strand of the new combined material.

The key is in how they are programmed and combined at the particle level, which in the Objet Connex 500 is a very small 80-picoliter (80-nanogram) drop. These printers 3D print multiple materials, each a custom blend created from two out of several possible base materials. They are combined during printing from two separate cartridges. The mix is determined by a jetting pattern based on a software algorithm that integrates them in specific, programmed mixes to achieve certain thermal and mechanical properties.

Different combinations can be placed in different parts of the 3D model to provide varying degrees of hardness, flexibility, or thermal resistance.

In the MIT/Stratasys project, Tibbits used Autodesk Cyborg, and Objet used VoxCad simulation tools to predict the behavior of multi-material structures, including where to use the expanding material. VoxCad predicts the behavior of small structures, the links programmed to bend when exposed to water, and Cyborg predicts the behavior of the overall structure formed of those links, said Dikovsky.

Tibbits is the director of MIT's new Self-Assembly Lab, which will develop the new technology jointly with Stratasys. Although the video of Tibbits' 2013 TED Talk was not online at press time, the video of a 2011 TED Talk Tibbits gave on self-assembly of furniture and buildings can be found here. In this video, he says MIT researchers have worked on a MacroBot and a DeciBot, which are large-scale, 8-ft- and 12-ft-long reconfigurable robots made of mechanical and electronic components.

Thanks for sharing this. I watched the underwater cube, then I watched Skylar's TED talk as well. When you think about a system like this, it makes sense that 3D printing (or some form of 3D manufacturing) and self-assembly go together--things we want in the world are mainly 3D, so they are assembled out of 3D parts (the printer that prints out of stacked sheets notwithstanding--they are still 3D--they have thickness!).

It is interesting to think about gravity as the main source of energy (potential energy) and building structures. In a sense, this is already done on a large scale or certain types of retaining walls. You have 3D blocks that fit together, and gravity provides the force to keep them together. I have seen some blocks for walls that are very large--think a concrete lego brick the size of a bale of hay. Some I have seen have bumps on one side and dents on the other, so they stack and won't move horizontally, and gravity does the rest.

On a smaller scale, I wonder what could be done with structures that respond to other sources, such as thermal, and pH, or even blood chemistry, and how those could be used in the body.

eafpres, thanks for the feedback. My April feature on self-assembly and self-reconfiguring robots will touch on several of these subjects. If you're interested in nanoscale self-assembly, I suggest you check out DNA origami and the Wyss Institute work on DNA 2D tiles and 3D bricks.

@Ann: Yes Ann I'm working on a AI project which involves some other electronic methodologies too. It can be used to detect the facial expressions which might or I'm trying to make it suited for ATM or even Healthcare and IT systems. I feel by doing this, the risk will get mitigated to a certain level.

a.saji, I have not personally used 3D printing. I've talked to people who have used it, mostly the high-end machines producing engineering prototypes and small-batch end-products for aerospace. Like any technology, it could have negative impacts on our world, which we've discussed in the comments sections to many stories in Design News.

@Ann: Yes there are always 2 sides of everything and same theory applies for this as well. I feel 3D printing is superb and will be the next big thing in IT but the fear is what if it goes in the wrong direction. What kind of negative impacts will it have ?

Many of the new adhesives we're featuring in this slideshow are for use in automotive and other transportation applications. The rest of these new products are for a wide variety of applications including aviation, aerospace, electrical motors, electronics, industrial, and semiconductors.

A Columbia University team working on molecular-scale nano-robots with moving parts has run into wear-and-tear issues. They've become the first team to observe in detail and quantify this process, and are devising coping strategies by observing how living cells prevent aging.

Many of the new materials on display at MD&M West were developed to be strong, tough replacements for metal parts in different kinds of medical equipment: IV poles, connectors for medical devices, medical device trays, and torque-applying instruments for orthopedic surgery. Others are made for close contact with patients.

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